Test airfoil



3 Sheets-Sheet 1 TEST AIRFOIL D. W. RABENHORST FIG. I

FIG. 3

Sept. 26, 1950 Filed Nov. 26, 1947 gwucmfo z DA V/D W. RABE/VHOR5 T /9 wSept. 26, 1950 D. w. RABENHORST TEST AIRFOIL 3 Sheets-Sheet 2 Filed Nov.26, 1947 8 4 1 Hu l l I I Ill/III! NP 1 J //H u lull umr awucnfoz W.RABENHORS 7' DA V10 Sept. 26, 1950 D. w. RABENHORST 2,523,481

TEST AIRF'OIL Filed Nov. 26, 1947 3 Sheets-Sheet 3 DAVID W ABEWHURSTPatented Sept. 26, 1953 um'nzo STATES, PATENT omen 2,523,481 T'Es'r AIRFO IL David W. Rabefihorst, Granliy, Co'nn., assignor is United Statesof America as represented by the Secretary of the N avy ApplicationNovember 26, 1947', Serial N 0.- 728,235

The present invention relates 'to "an improved test airfoil.

In wind-tunnel tests, it is often necessary to determine simultaneouslythe pressures acting at a multiplicity of places on the surfaces of anairfoil. These pressures are measured by means of manometers, or otherpressure indicators, connected to apertures in the surfaces of theairfoils by tulbes. One method of producing such an airfoil has been toform it to the desired external shape and leave an open interior inwhich are installed tubes leading from the apertures to the manometers.This method of construction is complicated, since the tubes have to beput in place one at a time and each one entails difficult connectionproblems caused by the restricted working space.

An object of the present invention is to provide a method of airfoilconstruction which will provide suitable ducts or tubes from theapertures to the end of the airfoil, such ducts being made during theconstruction of the airfoil.

Another object of the invention is to provide means for simultaneouslymeasuring the properties of a gas at different locations on the airfoil.

Another object of the invention is to provide an airfoil for testingwhich will be of relatively simple construction and which will be highlyefflcient in use.

Other objects will appear from the claims and description including thedrawings wherein;

Fig. 1 is an end view of one of a pair of blanks for an airfoil model;

Fig. 2 is a plan of the blank, showing the inner surface;

Fig. 3 is an end View demonstrating the method of assembly;

Fig. 4 is an end view ofa completed blank assembly, prior to milling,showing the method of forming the airfoil model;

Fig. 5 is an end view of a completed model;

Fig. 6 is a perspective view of a completed model; and

Fig. 7 is a longitudinal section of a modified form.

In the accompanying drawings, forming a part of this specification, andin which like numbers are employed to designate like parts throughoutthe same, the preferred article and method are illustrated.

Referring now to Figs. 1 and 2, a metal blank l0, having a ground planeouter face 12 and a ground plane inner face l4, together with a similarblank (not shown), form the principal com- 2 Claims. (Cl. 7 3 l47)ponents of an airfoil model. A number of small orifices iii are boredthrough the blank In at such angles and in such locations that they willbe normal to the surface and properly located on the surface of theairfoil section ll of the completed model, represented in Figs. 1 and lby a broken line l8 and in Fig. 5 by full line I8a.. After drilling anumber of orifices 56, parallel longitudinally oriented grooves 26 aremilled on the inner face it of the blank 40 from the orifices it to theend 22, spaced a distance therefrom, end 22 being the mounting end. Anumber of bores 24 are tapped through the mounting end to receiveexternal connections and are arranged at spaced intervals to intersectthe grooves.

A sheet of metal 26 is placed between the inner faces [4 of the matingblanks H], as shown in Fig. 3. The assembly is furnace brazed togetherto form a single unit, as shown in Fig. l, which said welding seals thegrooves 20 along the end 22. By this construction, the sheet 26 closesthe open grooves 20, converting them into semi-circular passages, ateach side of said sheet connecting the orifices IS with the tapped bores24.

In an alternative method of construction, the blanks III are pierced bya multiplicity of orifices l6 and tapped bores 24 after which thegrooves 20 on the inner face M are formed, connecting the orifices withtheir associated tapped bores but not extending to the mounting end 22.This method of construction eliminates the necessity of closing ends ofthe grooves during final assembly.

Referring now to Figs. 4, 5 and 6, the completed blank assembly, withthe exception of the mounting end, is ground to airfoil shape as definedby the broken lines l8 to produce an airfoil model complete with thepressure measuring orifices l6. Tubes 28 are screwed into the tappedbores 24 to provide external connections, as shown in Fig. 6. Suitableconnections are made between the ends of the tubes 28 and the pressureindicators when the model is tested.

If it is desirable to have more orifices than can be accommodated by theconstruction described above, additional thin sheets of metal 30 may beinterposed between the paired blanks IE, as shown in Fig. '7, toaccommodate additional longitudinal grooves 20a. connecting orifices Miaand bores Me.

In the construction of Fig. '7, the blanks ID are first drilled andgrooved as described above; then a sheet of metal 30 is alined witheach, by dowels or other similar means, and the addiplacing theseparating sheet 26 between the 0 sheets 30 and brazing the entireassembly as described above.

What is claimed is v 1. A device of the character described, comprisinga pair of blocks having mated faces, there "10 being a plurality oforifices through said blocks,

there being a plurality of measuring device con nections, eachcomprising a bore having atapped end, there being a plurality of groovesfashioned-L on the mating faces of said blocks and extending 15 fromsaid orifices to said connections, and a sheet of material interposedbetween saidblo'cks' to form enclosed passages out of said groovesr' 2.An airfoil for test, including a pair of blocks eachmaving a mountingendand a foil section, 0

each of said foil sections being formed with a plurality of testorifices, and having a surface designed to mate with a correspondingsurface on the other, said mating surfaces of said foil sections havinggrooves communicating between the mounting ends and said orifices, aseparating sheet. between said sections, the sections and saidseparating sheet being joined together to form a single airfoil unithaving a plurality of orifices ;and said grooves communicating betweensaid orifices and the exterior of said sections.

DAVID W. RABENHORST.

REFERENCES CITED UNITED STATES PATENTS Name Date Heuver. Dec. 11, 1945Number

